Art of manufacturing thiazols



" Patented July 6, 1926.

' UNITED STATES PATENT OFFICE.

LORINB. SEBRELL AND CLAYTON W. BEDFORD, OF AKRON, OHIO, ASSIGNORS TO THEGOODYEAR TIRE &: RUBBER COMPANY, OF AKRON, OHIO, A CORPORATION OF ART or"MANUFACTURING rrrmzons.

No Drawing. Original application filed December 7, 1921, Serial No.520,689. Divided and application filed November 30, 1923, Serial No.677,877, Patent No. 1,544,688, dated July 7, 1925. Divided.

and this application filed April 12, 1924. Serial'No. 706,079.

- This application a division of application Serial Number 677,877,Patent No. 1,544,688, issued July 7, 1925.

Our invention relates to accelerators of 5 the vulcanization of rubberand it has, for

its primary object, the provision of accelerators of high curing power,which may be prepared in a manner best adaptedto facilitate theirproduction.

0 In Patents Numbers 1,371,662; 1,371,663

and 1,371,664, issued March 15, 1921, a number of accelerating reagentsare described as the reaction products of sulfur and nitrogen-containingbodies. In this applica- .6 tion is is our desire to set forth specificingredients, or reagents, which are especially active accelerators andwhich result from reactions of sulfur with thiocarbanilid.

As set forth in the above,mentioned pat- :0 ents, accelerators ofconsiderable commercial value may be prepared by efi'ecting' certainreactions, such as the reaction of sulfur with thiocarbanilid, beforechemicals are incorporated in the rubber mix and subjected to the heatof vulcanization. By establishing proper conditions of temperature andadmixture of the reacting materials, a satisfactory accelerator isassured, whereas during vulcanization, such 30 idealconditions might notobtain.

as ized.

Jacobson and Frankenbaker, Ber. 24, 1400 (1891) and others, havedescribed mercaptobenzothiazol the By our present invention we disclosethe specific reaction products which are responsible for the high curingpower of the reaction products of sulfur with thiocarbanilid. Thedesired accelerators may, consequently, be more elliciently produced andutilized to best advantage, by their isolation and use in a pure orsemi-pure state.

It will be appreciated, of course, that theclass of reactions involvedin this preparation is not unlike many others in that its rate may beaccelerated either negatively or positively by an appropriate variationin temperature or pressure, or both. Thiocarbanilid may be assumed to bean equilibrium with its tautomeric form CcHgNH-C-SH Cam WhenB issulfurized and aniline eliminated,

' l-mercaptobenzothia'zol is formed, as shown by the following reaction:

as the sulfur reaction product of phenyl mustardoil N=o=si It is alsowell known that thiocarbanilid decomposes under the influence of heatinto found that both of these reactions occur when thiocarbanilid isheated with sulfur phenyl mustard oil and aniline. We havemercaptobenzothiazol and aniline.

and that the chief reaction products are Anilidobenzothiazol,thioanilines, hydrogen sulfide, carbon bisulfide and other products arealso formed.

-We have also discovered that an excess of sulfur oxidizesmercaptobenzothiazol to form benzothiazyl disulfide,

Benzothlazyl disulfide polysulflde Extensive experiments have definitelyestablished that the free mercaptan, its normal or basic lead or zincsalts, its disulfide or disulfide polysulfide are all desirableaccelerators for the vulcanization of rubber by sulfur. Furthermore,depending upon the rubber compound in which they are to be utilized,they may be isolated and employed in a pure or nearly pure condition.The reaction products of thiocarbanilid and sulfur may be separated fromaniline before their use, or the maybe utilized without isolating any oft e resulting constituents.

It has also been determined that mercaptobenzothiazol will react furtherwith sulfur and that a second substitution of sulfur in the nucleus mayoccur. If this sulfuration process is not permitted to proceed too far,an accelerator of high power may still be obtained.

In order to illustrate the merits of accelerators prepared in accordancewith our invention, we have vulcanized rubber under different degrees ofsteam pressure and tested the physical properties of the resultingproducts; In addition to comparing thesecelerators with each other,such' tests prove the desirability of such accelerators with respect tosimilar reagents known to those familiar with the art. a

In the following chart is shown the time required to cure rubber at 20pounds and 40 pounds of steam pressure. Although the usual curingtemperature adopted is represented by 40 pounds steam pressure, thelower steam pressure was also utilized because the trend of present daypractice is to reduce the temperature.

In the following examples, a mixture was utilized which consisted of:

Parts. Smoked sheet Zinc oxide 5 Sulfur 3. 5

One part of mercaptobenzothiazol was used and equivalent proportions ofits derivatives to correspond to one molar weight of the originalmercaptan.

The fact that the above accelerators may be isolated from the reactionproducts of sulfur and nitrogen-containing bodies permits of theirpurification, which aids in reducing the length of time necessary toeffect the best cure, as well as to avoid the softening action of thethioanilines which otherwise are present.

Although we have specifically described accelerators that may beutilized in promoting the vulcanization of rubber and stated ourtheories with regard thereto, it is obvious that minor changes may bemade in the application of the principles of our invention withoutdeparting from the spirit and scope thereof and we desire, therefore,that only such limitations shall be imposed as are indicated in theappended claims.

What we claim is 1. A method of making thiazols that comprises heatingits corresponding substitute thiourea in the presence of sulfur.

2. A method of making aryl thiazols that comprises heating an arylsubstituted thiourea in the presence of sulfur.

3. A method of making a mercaptoarylthiazol that comprises heating underpositive pressure an a l substituted thiourea in the presence of su fur.

4. A method of making 1 mercaptobenzothiazol that comprises heatingthiocarbanilid in the presence of sulfur.

5. A method of making mercaptobenzothiazol that comprises heatin underpositive pressure thiocarbanilid with sulfur.

6. A method of making mercaptobenzothiazol disulfide that comprisesheating thiocarbanilid in the presence of sulfur to forin amount ofsurfur in excess of that suificient mercaptobenzothiazol, and thenheating the to form mercaptobenzothiazol. mercaptobenzothiazol in thepresence of an In witness whereof we have hereunto excess of sulfur.signed our names.

7. A method of makin mercaptobenzothiazol disu1fidepo1ysulfi e thatcomprises LORIN B. SEBRELL.

heating thiocarhanihd in the presence of an r CLAYTON W. BEDFORD. I

